Optical scanner having enhanced item side coverage

0001The present invention relates to optical scanners and more specifically to an optical scanner having enhanced item side coverage.

0002U.S. Patent No. 5,229,588 to Detwiler et al. discloses a dual aperture optical scanner which includes horizontal and vertical apertures. The scanning light beams from a single laser diode pass through these apertures to provide coverage for up to four sides of a scanned item: the side facing the vertical aperture (front), the side facing the horizontal aperture (bottom), and the left and right sides.

0003While this scanner requires much less item orientation than a single aperture scanner, it is not capable of scanning the top and rear sides of scanning items. It is an object of the invention to provide an optical scanner which is capable of scanning as many as five sides of a typical merchandise item.

0004In accordance with the invention there is provided a bar code scanning system comprising a housing having first and second windows arranged generally orthogonally to one another, a laser source, a rotatable mirror polygon, and first and second sets of plane pattern mirrors arranged to provide scanning beams which illuminate an object to be scanned with a plurality of intersecting lines, characterized by a third set of plane pattern mirrors the three sets of pattern mirrors being arranged to provide two groups of scanning beams (I,II) which pass through the first window and a further group of scanning beams (III) which passes through the second window.

0005Preferably the three groups of scanning beams together illuminate the object from angles corresponding to five of the six codes of a cube.

0006The invention will now be described by way of example only with reference to the accompanying drawings, in which: <ul id="ul0001" list-style="none" compact="compact"><li>Fig. 1 is a block diagram of the optical scanner having enhanced item side coverage of the present invention;</li><li>Fig. 2 is an exterior perspective view of the scanner of the present invention, including a reference coordinate system for the group of pattern mirrors within the scanner of the present invention;</li><li>Fig. 3 is an interior perspective view of the scanner of the present invention;</li><li>Fig. 4 is a sectional view of the scanner of the present invention along lines 4-4 of Fig. 3;</li><li>Fig. 5 is a reference coordinate system for determining one-suitable orientation for the group of pattern mirrors within the scanner of the present invention;</li><li>Fig. 6 is a plan view of the scan pattern emanating upwardly from a horizontal aperture;</li><li>Fig. 7 is a plan view of a first scan pattern emanating outwardly from a vertical aperture;</li><li>Fig. 8 is a plan view of a second scan pattern emanating outwardly from the vertical aperture;</li><li>Fig. 9 is a plan view of the combined first and second scan patterns of Figs. 7 and 8; and</li><li>Fig. 10 is a perspective view of a laser assembly showing two lasers.</li></ul>

0007Referring now to Fig. 1, a point-of-service (POS) system 10 includes optical scanner 11 and POS terminal 13.

0008POS terminal 13 receives transaction data, for example, in the form of SKU numbers from scanner 11 and completes a transaction by finding price data for the SKU numbers in a price-lookup data file.

0009Scanner 11 of the present invention includes laser 12, optical transceiver 14, mirrored spinner 16, pattern mirrors 18, deflector mirror 19, photodetector 20, and control circuit 21. Laser 12 includes a laser diode or other suitable laser source.

0010A focusing lens or lenses and a collimating aperture are also preferably used to produce a focused and collimated laser beam 22. In the preferred embodiment, the laser diode emits visible light within a wavelength range of 670-690nm and the collimating aperture and focusing lens produce a beam 22 having a beam waist of 220 microns in the center of the read zone. Other wavelengths and beam waists may be suitably employed.

0011Beam 22 passes through optical transceiver 14, which includes a mirrored collecting surface and an aperture for passing beam 22. The mirrored collecting surface preferably has an ellipsoidal or other curved surface.

0012Beam 22 contacts mirrored spinner 16, which preferably has four planoreflective mirrored facets 108-114 for producing scanning beams 24 (Fig. 3). Four facets were chosen as an optimal compromise between the increased line length created by using three facets and the increased rastering provided by spinners having more than four facets.

0013Scanning beams 24 impact pattern mirrors 18, which produce a plurality of scan lines 26. In the preferred embodiment, pattern mirrors 18 are preferably flat and produce forty scan lines 26 for each complete revolution of mirrored spinner 16. Advantageously, all forty scan lines 26 are preferably produced by only one laser 12 and motor 17. Use of a greater or lesser number of scan lines and pattern mirrors will be apparent to those skilled in the art.

0014Some scan lines 26 pass through a substantially horizontal aperture 28 and some pass through a substantially vertical aperture 30 in scanner housing 32 on their way to bar code label 34 on merchandise item 36. Substantially vertical aperture 30 is preferably oriented at 5¾ degrees from a vertical plane. The choice of angle is chosen to optimize the scan volume and line length of the scan lines. It is desirable to achieve a ratio of the minimum length of the longest scan line to the maximum length of the shortest scan line as close as possible to one. At about ten degrees, scanning is adversely impacted for the configuration of pattern mirrors 18 illustrated herein.

0015According to the present invention, scan lines 26 are divided into three groups. Scan lines within a first group (Group I) emanate outwardly and downwardly from vertical aperture 30 to illuminate the top and customer sides of an item.

0016Scan lines within a second group (Group II) emanate outwardly from aperture 30 as three sub-groups to illuminate the customer side (Sub-group IIa), the customer and leading sides (Sub-group IIb), and customer and trailing sides (Sub-group IIc).

0017Scan lines from the third group (Group III) emanate upwardly from horizontal aperture 28 as three sub-groups to illuminate the bottom (Sub-group IIIa), leading side (Sub-group IIIb), and trailing side (Sub-group IIIc).

0018Reflected light 37 is redirected by pattern mirrors 18 towards spinner 16, which further directs it towards optical transceiver 14. Optical transceiver 14 directs and focuses reflected light 37 at deflector mirror 19, which further directs reflected light 37 towards photodetector 20. Photodetector 20 generates electrical signals representing the intensity of reflected light 37.

0019Control circuitry 21 decodes bar code label 34 and controls power to laser 12 and motor 17. Control circuitry 21 may remove power from laser 12 and motor 17 to increase the longevity of laser 12 and motor 17. When scanner 11 is equipped with two lasers (Fig. 10), control circuitry 21 alternates power removal from lasers 140 and 142. For example, control circuitry 21 may remove power from laser 140 during one complete revolution of spinner 16, and remove power from laser 142 during the following revolution.

0020Turning now to Fig. 2, scanner 11 is shown in perspective. Horizontal aperture 28 is located within substantially horizontal surface 38 of housing 32. Vertical aperture 30 is located within substantially vertical surface 40.

0021Preferably, scanner 11 may be easily adapted to fit in a typical checkout counter 42. Standard dimensions for apertures in checkout counters like checkout counter 42 are about eleven inches in length (i.e., in the direction of item flow), twenty inches in width (i.e., in the direction across the direction of item flow), and five inches deep. Thus, despite its improved scan coverage, scanner 11 easily fits within standard apertures. This is due to the optimal size and arrangement of components within scanner 11.

0022It is envisioned that top surface 38 be made substantially flush with the top surface 44 of counter 42, and also include a scale 43. Scanner 11 is installed within checkout counter 42 so that substantially vertical aperture 30 faces a store employee.

0023Referring now to Figs. 3 and 4, the presently preferred arrangement of scanner components is shown in more detail. Laser 12 is preferably oriented at thirtyfive degrees from the horizontal or X-axis as shown in Fig. 2. Laser 12 is mounted within a bracket 15 which attaches to the lower wall of scanner 11. Beam 22 contacts planoreflective surfaces 108-114 of mirrored spinner 16 (Fig. 4). Spinner axis 116 is preferably oriented at twenty-two and a half degrees from a vertical or Z-axis. Facets 108-114 are preferably oriented at two and half degrees, four degrees, seven degrees, and eight and a half degrees, respectively, from spinner axis 116. These angles cause spinner 16 to generate four different sets of scan lines (Table III below) and are chosen to balance spinner 16 as much as possible consistent with the goal of generating four different sets of scan lines.

0024Pattern mirrors 18 are all preferably flat mirrors. Scanning beams 24 from spinner 16 impact a first set of mirrors 50-72 and reflect therefrom to a second set of mirrors 74-98. Mirrors 80-98 within the second set further direct beams 24 to a third set of mirrors 100-106.

0025The reference coordinate system for mirrors 50106 is shown in Figs. 2 and 5, and includes X, Y, and Z axes, with the Z-axis being out of the page. Coordinates Xm, Ym, and Zm are measured in inches, and angles Xr and Yr, are measured in degrees, with positive angles being measured in a counter-clockwise direction. Pattern mirrors 18 are positioned or located with respect to this coordinate system as described below. Each mirror is first oriented parallel to the X-Y plane through a point (Xm, Ym, Zm) . Each mirror is rotated through an angle Xr about a line X' parallel to the X-axis and containing the point (Xm, Ym, Zm). Each mirror is rotated through an angle Yr about a line Y' parallel to the Y-axis and containing the point (Xm, Ym, Zm). Thus, these five variables uniquely define planes for mirrors 50-106 and are shown in Table I. Presently preferred values are shown.

0026Origin O is defined such that: <ul id="ul0002" list-style="none" compact="compact"><li>X=0 is on the centerline of the scanner;</li><li>Z=0 is on the centerline of the scanner; and</li><li>Y=0 is on the substantially horizontal surface 38.<img file="EP0772147A2_D0001.tif" /><img file="EP0772147A2_D0002.tif" /></li></ul>

0027Table II shows orientation and location data for the laser, spinner, and photodetector: <tables id="tabl0001" num="0001"><table frame="all"><title>Table II:</title><tgroup cols="4" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">Component</entry><entry namest="col2" nameend="col2" align="center">Xm</entry><entry namest="col3" nameend="col3" align="center">Ym</entry><entry namest="col4" nameend="col4" align="center">Zm</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">Laser</entry><entry namest="col2" nameend="col2" align="char" char=".">-4.050</entry><entry namest="col3" nameend="col3" align="char" char=".">-3.940</entry><entry namest="col4" nameend="col4" align="char" char=".">+0.000</entry></row><row><entry namest="col1" nameend="col1" align="center">Spinner</entry><entry namest="col2" nameend="col2" align="char" char=".">-6.875</entry><entry namest="col3" nameend="col3" align="char" char=".">-2.175</entry><entry namest="col4" nameend="col4" align="char" char=".">+0.000</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">Photodetector</entry><entry namest="col2" nameend="col2" align="char" char=".">-4.645</entry><entry namest="col3" nameend="col3" align="char" char=".">-4.580</entry><entry namest="col4" nameend="col4" align="char" char=".">+0.000</entry></row></tbody></tgroup></table></tables>

0028In operation, laser beam 22 strikes each facet of mirrored spinner 16 in sequence. Table III summarizes the facet and mirrors involved in generating the forty scan lines (Figs. 6-9) during one revolution of spinner 16. The forty scan lines are arranged in the sequence in which they are generated as spinner 16 rotates in a counter-clockwise direction as viewed from above. <tables id="tabl0002" num="0002"><img file="EP0772147A2_D0003.tif" /></tables><tables id="tabl0003" num="0003"><img file="EP0772147A2_D0004.tif" /></tables><tables id="tabl0004" num="0004"><img file="EP0772147A2_D0005.tif" /></tables>

0029Referring now to Figs. 6-9, horizontal scan pattern 120, vertical scan pattern 122, and top-down scan pattern 124 are shown. Some of scan lines 26 appear to be curved. This is because scan beams 24 from spinner 16 do not lie in a flat plane; they lie on the surface of a shallow cone. The curvature of scan lines 26 represents the intersection of that cone and a particular intersecting plane (e.g., an aperture). The amount of curvature depends on the relative angle between the projected cone and this plane. Since the cone of light projects at different angles for the various scan lines 26, scan lines 26 may appear to have different curvatures.

0030Horizontal scan pattern produces Group III scan lines which emanate from horizontal aperture 28. Scan lines within Sub-group IIIa include B1-B4, C1-C4, D1-D4, and E1-E4. Scan lines within Sub-group IIIb include AlA. Scan lines within Sub-group IIIc include F1-F2. Side 130 of aperture 28 is the operator side.

0031Vertical scan pattern 122 (Fig. 7) produces Group II scan lines which emanate from vertical aperture 30. Scan lines within Sub-group IIa include O1-O2 and P1-P2. Scan lines within Sub-group IIb include G1-G2. Scan lines within Sub-group IIc include J1-J2. Side 132 of aperture 30 is the top side.

0032Top-down scan pattern 124 (Fig. 8) produces Group I scan lines which emanate from vertical aperture 30 and include scan lines H1-H2, I1-I2, K1-K2, L1-L2, M1M2, and N1-N2.

0033Fig. 9 illustrates the combined scan lines emanating from vertical aperture 30.

0034Turning now to Fig. 10, bracket 15 may contain two lasers 140 and 142. Lasers 140 and 142 are preferably combined such that their laser beams are co-linear. This is accomplished by using a transparent window 144 with one partially reflective side 146. Window 144 is mounted on a support member and placed in front of laser 140 so that its beam strikes window 144 at a forty-five degree incidence angle. Laser 142 is oriented so that its beam is orthogonal to the beam of laser 140 and has a forty-five degree incidence angle with window 146. The resulting co-linear beams of both lasers 140 and 142 are parallel to and substantially co-linear with the path of the beam of laser 12 in the single-laser embodiment.

0035Additional lasers may be easily incorporated by adding additional windows. Bracket 15 may be easily modified to accommodate three or more lasers.

0036Preferably, lasers 140 and 142 are substantially identical and have substantially identical foci. The foci are preferably offset to increase the effective depth of field of scanner 11. Alternatively, the foci of lasers 140 and 142 may be different to enable scanner 11 to read bar codes of various spatial frequencies.